1. Field of Invention
This invention is directed to a device for separating materials of different density, from a flowing stream of fluid which may contain solids, liquids and gases. The device may be readily transported to remote locations such as oil or gas wells to remove solids, for example sand, from fluid that is used at the well site for various purposes and requires treatment after use.
2. Description of Related Art
Currently sand separation equipment is used following fracturing or well stimulation operations. The sand separators are placed in line in front of the choke manifold and other production piping or equipment. This is done in an effort to avoid erosive damage that can be caused by the sand flowing at high velocities through the equipment. In addition some of the equipment can become damaged or plugged up when the sand settles out inside of the equipment piping or pipe lines. This sand can also damage the equipment beyond repair or can result in costly and extensive cleaning operations to the piping and equipment. The equipment that is currently used to filter or separate these contaminates, whether it be sand or other contaminants use one of two technologies.
The first technology uses hydra cyclone separations or basically uses the velocity of the fluid to sling the sand to lower velocity areas where the sand can settle or separate into a catch pot so it may be dumped or purged from the system. The problem with this technology is, for the system to work the fluid has to be accelerated and directed to a flow path that causes a swirling affect that then slings the sand particles to the outside of the flow path. This increase in velocity accelerates the abrasiveness of the sand and requires that the components be made out of materials that can withstand the abrasion. These materials although resistant do not stop the abrasion and only prolong the wear. Once however the components have been worn beyond their design tolerances they lose their effectiveness and the separators cease to work. This failure can be unpredictable and catastrophic. With new drilling technologies the current flow rates and pressures make this method of separation undesirable.
The second technology that is currently used is large vertical columns or settling pots. This technology is much more robust than the first and uses the increased diameter of the settling pots to slow the fluid velocity below the settling rate of the sand. This technology works very well for low fluid rates with large or dense sand particles that are being separated under low pressures. Basically the sand falls out of the fluid at a faster rate than the fluid is being pumped through the assembly. The sand then settles into the bottom part of the assembly and is purged from the system into holding tanks or pits where it can be disposed of. The problem with this technology is the higher the flow rate is, the larger the settling pot has to be for separation to occur. This also holds true for the smaller particles of sand or material as well, the slower it falls through the fluid the less separation that occurs. Therefore these types of separators although robust are not very efficient with higher flow rates and smaller sand particles. The other problem is when using a settling pot, as the pressure increases so does the wall thickness of these pots. Some of these pots are so large that they are difficult to transport and set up and to work on. These vertical columns are also impacted greatly by any type of gas production from the well. Because they rely on reduced velocity for separation to occur anything that causes the velocity to increase can have significant effects on the ability of the separators to work. Therefore as the gas enters into the larger chamber and expands reduced separation occurs and more sand is carried on through the system. In a vertical column the gas races toward the top much as a balloon being released below the water would. This acceleration of gas and fluid caused by high gas flow rates make these separators ineffective in removing contaminates from the fluids.
A variation of the second technology is disclosed in U.S. Pat. No. 7,429,332. A separator is disclosed that includes an inclined vessel having one or more inlet ports 112. The device is designed for solids and liquids. A convection cell 120 forms within the vessel. This device is somewhat effective in separating heavier sand particles in a liquid stream with no gas however it would not be as effective is separating out finer sand particles and in situations where gas is present in fluid. The patent uses the convection effect to cause rotation of the fluid allowing additional retention time for the particle to gravitationally separate from the fluid. This use of convection is slow and not very efficient. It works best on the larger heavier particles and is the reason that in one of the drawings twenty to thirty cells are connected in series and in parallel. This method also generates turbulence within the fluid flow or rotation caused by the convection reducing the effectiveness of the gravitational separation. An indication that this design does not work well with smaller size particles of sand is that in some of the disclosed embodiments a sand filter is used to separate the smaller medium from the fluid mixtures.